rce_workflow (schueltke): fixed mission_energy paths
- fixed mission_energy path problem by generic paths adapted to new XML structure
This MR is directly linked to issue #4 and notes 2731903 and 2731904
To test it pull code from bug_fix/mission_energy_paths and copy src folder into your local UNICADOworkflow installation; compare output of reporting/sizing_loop_results.csv in the column of m_mission_fuel (before it was 0, now it should be something about 15xxx)